The Prognostic Importance of Serum Sodium for Mortality among Critically Ill Patients Requiring Continuous Renal Replacement Therapy.

BACKGROUND Serum sodium derangement is common in critically ill patients requiring continuous renal replacement therapy (CRRT). We aimed to assess the association between serum sodium before and during CRRT with mortality. METHODS This is a historical cohort study of 1,520 critically ill patients receiving CRRT from December 2006 through November 2015 in a tertiary hospital in the United States. Using logistic regression analysis, we used serum sodium before CRRT, mean serum sodium, and serum sodium changes during CRRT to predict 90-day mortality after CRRT initiation. RESULTS Compared with the normal serum sodium levels, the odds ratio (OR) of 90-day mortality in patients with serum sodium before CRRT of 143-147 and ≥148 mmol/L were 1.45 (95% CI 1.03-2.05) and 2.24 (95% CI 1.33-3.87), respectively. There was no significant increase in 90-day mortality in serum sodium of ≤137 mmol/L. During CRRT, the mean serum sodium levels of ≤137 (OR 1.41; 95% CI 1.01-1.98) and ≥143 mmol/L (OR 1.52; 95% CI 1.14-2.03) were associated with higher 90-day mortality. The greater serum sodium changes during CRRT were associated with higher 90-mortality (OR 1.35; 95% CI 1.21-1.51 per 5-mmol/L increase). CONCLUSION Before CRRT initiation, hypernatremia and during CRRT, hypo- and hypernatremia were associated with increased mortality.